U.S. forces are massing on the Pakistan border in eastern Afghanistan amid reports of an imminent drone missile offensive against fighters from the feared Haqqani Network, a Taliban faction which operates from safe havens in Pakistan’s North Waziristan Agency, Pakistan Army sources have confirmed.

The scale of the American build-up, including helicopter gunships, heavy artillery and hundreds of American and Afghan troops, caused panic in north Waziristan where tribal militias who feared they could be targeted gathered in the capital Miranshah to coordinate their response.

Local officials in the Federally-Administered Tribal Areas (FATA) warned that Pakistan’s armed forces would repel any incursion across the border by American forces, but military sources in Islamabad and Afghan officials suggested the build-up was part of a coordinated operation.